| Autor: |
Franey, J. P., Graedel, T. E., Gualtieri, G. J., Kammlot, G. W., Kelber, J., Malm, D. L., Sharpe, L. H., Tierney, V. |
| Zdroj: |
Journal of Materials Science; September 1981, Vol. 16 Issue: 9 p2360-2368, 9p |
| Abstrakt: |
Among the important properties of conductive silver-epoxy pastes are their relatively low internal electrical resistance and their low rate of sulphidizing relative to pure silver. To investigate these properties in more detail and to gain understanding of the physical mechanisms involved, paste and bulk silver samples have been exposed to a controlled corrosive atmosphere of hydrogen sulfide and water vapour in purified air. The exposed samples were then analysed by a variety of surface and bulk techniques. The results demonstrate that (1) although the contact resistance of the bulk silver is initially much lower than that of the conductive paste, it increases much more rapidly with long exposure to corrosive atmospheres than that of the paste; this is especially true at low contact probe forces, (2) the hydrogen sulfide permeation constant through a free-standing film of unsilvered paste is (7.0±0.3)×10-2 barrers: sufficiently low that transport of H2S into the bulk paste is strongly inhibited, (3) silver flakes projecting outward from the surface of the paste have little or no resin coating. Corrosion thus occurs on the surface of the material but is inhibited within the material. The relative softness of the material allows contact probe penetration into the uncorroded bulk matrix. As a result, little decrease in the conductivity of the paste occurs even after extended exposures to a corrosive environment. |
| Databáze: |
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